Using a small fuel cell for high octane fuel for nitrous only how would I calculate how much fuel would be would be used?

I'm researching a fuel cell for my nitrous setup and would like to use the smalles possible size I can.

I'm tentatively planning a 125HP shot dry (completely hidden) and then another 100 to 150 shot wet with the high octane fuel.

So if someone see's that portion I can just unhook it so that I'm "supposedly" not running nitrous anymore.


Mike